The present invention relates to a method and apparatus for reading printed data from a head in a head stack assembly of a disc drive. In particular, the present invention relates to a method and apparatus for reading and recording printed alphanumeric data (e.g. a serial number or part identification number) applied to a head in a head stack assembly.
A head stack assembly of a disc drive supports a plurality of heads for selectively positioning the heads relative to selected data tracks on magnetic discs for reading information from and writing information to the magnetic discs. The head stack assembly is movably supported relative to the magnetic discs for selectively aligning the heads of the head stack assembly over a selected group of data track(s) (or cylinders) on the discs.
Each head in the head stack assembly includes a slider which supports a transducer for reading and writing data on the magnetic discs. The slider includes a leading end and a trailing end. The transducers are typically positioned at a trailing end of the slider. During manufacture, alphanumeric data (e.g., serial or part number) is printed (typically laser etched) on the leading end of the slider. This alphanumeric data is used to track and record manufacturing data, such as lot number, manufacture date(s), and plant of assembly for the heads.
The alphanumeric data etched on a printed surface of a slider may be read from individual heads prior to assembly of the head stack. It is also desirable to read alphanumeric data from a printed surface of the heads of an assembled head stack assembly. The data has, in the past, been read manually by aligning the printed surface of each head with a microscope or other magnification device. Since the printed surface is on a leading end of the slider, it is difficult to align the head stack assembly so that the printed surface of the heads may be read.
In particular, in order to read or decipher the data on the printed surface, it is necessary to precisely orient the head stack assembly so that the data on the printed surface is visible by the magnification device. This process can be difficult and time consuming since each head must be precisely aligned relative to the magnification device so that the printed data is visible to the magnification device. It also may be necessary to focus individual portions of the alphanumeric data separately in order to compile and record the entire part identification or serial number for each individual head since it may not be possible to view (under magnification) the entire printed surface of a head at once. Repeat handling of the head stack assembly during this process of reading information from the heads may cause damage and wear to the heads and the head stack assembly.
Thus, the method of individually aligning and focusing the printed surface of each head in the head stack assembly to read printed data is time consuming and expensive, and may cause damage to the head stack assembly.